1. The Field of the Invention
The present invention relates to dispersion resistant digital optical transmitters.
2. The Relevant Technology
The quality and performance of a digital transmitter is determined by the distance over which the transmitted digital signal can propagate without severe distortions. This is typically characterized as the distance over which a dispersion penalty reaches a level of about 1 dB. A standard 10 Gb/s optical digital transmitter, such as an externally modulated optical source (e.g., a laser), can transmit up to a distance of about 50 km in standard single mode fiber, at 1550 nm, before the dispersion penalty reaches the level of about 1 dB. This distance is typically called the dispersion limit.
The Bit Error Rate (BER) of an optical digital signal after propagation though fiber, and the resulting distortion of the signal, are determined mostly by the distortions of a few bit sequences. The 101 bit sequence, and the single bit 010 sequence, are two examples of bit sequences that have high frequency content and tend to distort most after dispersion in a fiber, leading to errors in the bit sequence. Transmission techniques that can alleviate the distortion for these bit sequences increase the dispersion tolerance of the entire data pattern.
In view of the foregoing it would be advancement in the art to provide an apparatus and method for increasing the dispersion tolerance of an optical digital transmitter, particularly for high-frequency data.